The present invention relates to an electromagnetic coupling apparatus for interrupting power transmission or more in particular to an electromagnetic coupling apparatus effectively used with an electromagnetic cluch for transmitting engine power to a refrigerant compressor of an automobile cooling system.
In conventional electromagnetic clutches used with a refrigerant compressor of the automobile cooling system shown in FIG. 1, the terminal 1a of a magnet coil 1 and a lead wire 25 of an electric connector 21 are soldered to each other on the inside of a yoke 2 (at the position shown by A in FIG. 1), and epoxy resin 3 is filled between the yoke 2 and the coil 1. The lead wire 25 which is supported by a rubber bushing 22 is adapted to be led out of the fixing member 4 and the yoke 2.
This type of conventional electromagnetic clutches is difficult to assemble automatically by machine due to the dual disadvantages that the soldering is effected at position A within the yoke 2 and that the soldering is required with the lead wire 25 which is comparatively soft and difficult to support in position securely. Thus the electromagnetic clutches are unavoidably assembled manually, resulting in a low working efficiency.
Further, a small circular hole is formed at part or the yoke 2 supporting the magnet coil 1, and a pin is driven and secured in the front housing of the compressor. This pin is fitted with the small hole so that the yoke 2 is securely fixed on the front housing.
Nevertheless, the pin is likely to come off due to the strong vibrations applied to the compressor. Once this pin comes off the hole, the yoke 2 supporting the magnet coil 1 rotates, with the result that the lead wire of the magnet coil is tensioned and broken. The breakage of the magnet coil lead wire makes the electromagnetic clutch inoperative, thereby causing a serious accident.